<p>The configuration of the tungsten cathode is a critical factor influencing the physical characteristics of the TIG arc. Changing the configuration of the tungsten cathode can adjust the shape of the arc, which in turn changes the distribution of current density applied on the anode surface. This will lead to changes in the thermal and force distribution on the anode surface, which will ultimately affect the weld formation. This paper focuses on the trapezoidal plate tungsten cathode. The anode current density is measured using the tungsten probe method. The control mechanism and influence are explained by comparing the anode current density distribution of the trapezoidal plate tungsten cathode with different tip angles and tip platform lengths. The results indicate that the influence of the trapezoidal plate tungsten cathode configuration on tip discharge effect is the main factor causing the expansion of the cathode arc root. The trapezoidal plate tungsten cathode configuration causes the arc shape to expand, which in turn increases the range of anode current density distribution. This leads to the reduction in the maximum-value of the anode current density of the trapezoidal plate tungsten cathode, and the concentration of the current density distribution also decreases accordingly. Using the trapezoidal plate tungsten cathode with a larger tip angle and a longer tip platform length can effectively weaken the tip discharge effect. This will further expand the cathode arc root and increase the range of anode current density distribution. This will also lead to a further decrease in maximum-value and concentration of the anode current density distribution. At the same time, the weakening of the anode current density leads to a decrease in both electron absorption heat and arc pressure. The concentration of thermal and force distribution will also be significantly lower, which will result in a smaller weld penetration depth and a larger weld width.</p>